/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.sdk.values;



import java.lang.reflect.ParameterizedType;

import java.lang.reflect.Type;

import java.lang.reflect.TypeVariable;



import static com.bff.gaia.unified.vendor.guava.com.google.common.base.Preconditions.checkArgument;



/**

 * Captures a free type variable that can be used in {@link TypeDescriptor#where}. For example:

 *

 * <pre>{@code

 * static <T> TypeDescriptor<List<T>> listOf(Class<T> elementType) {

 *   return new TypeDescriptor<List<T>>() {}

 *       .where(new TypeParameter<T>() {}, elementType);

 * }

 * }</pre>

 */

public abstract class TypeParameter<T> {

  final TypeVariable<?> typeVariable;



  public TypeParameter() {

    Type superclass = getClass().getGenericSuperclass();

    checkArgument(superclass instanceof ParameterizedType, "%s isn't parameterized", superclass);

    typeVariable = (TypeVariable<?>) ((ParameterizedType) superclass).getActualTypeArguments()[0];

  }



  @Override

  public int hashCode() {

    return typeVariable.hashCode();

  }



  @Override

  public boolean equals(Object obj) {

    if (!(obj instanceof TypeParameter)) {

      return false;

    }

    TypeParameter<?> that = (TypeParameter<?>) obj;

    return typeVariable.equals(that.typeVariable);

  }



  @Override

  public String toString() {

    return typeVariable.toString();

  }

}